A hybrid image allows multiple image interpretations to be modulated by the viewing distance. Originally, it can be constructed by combining the low and high spatial frequencies of two different images. The original hybrid image synthesis was limited to similar shapes of source images that were aligned in the edges, e.g., faces with a different expression, to produce an effective double image interpretation. In our previous work, we proposed a noise-inserted method for synthesizing a hybrid image from dissimilar shape images or unaligned images. In this work, we propose a novel method for adding an image to be seen from a middle viewing distance. The middle-frequency (MF) image is extracted by a special bandpass filter, which generates ringing while extracting only specified frequency bands. With this method, the middle frequency should be perceived as a meaningless pattern when viewed from a far distance and close up. A parameter tuning experiment was performed to determine the suitable cutoff frequencies for designing the filter for the MF image. We found that ringings of a suitable size could be used to make the middle frequency less noticeable when seen from far away.

中文翻译：

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三种内容的混合图像。

混合图像允许通过观看距离来调制多种图像解释。最初，它可以通过组合两个不同图像的低空间频率和高空间频率来构造。原始的混合图像合成仅限于源图像的相似形状，这些形状在边缘对齐（例如，表情不同的人脸），以产生有效的双重图像解释。在我们以前的工作中，我们提出了一种噪声插入方法，用于从形状不同的图像或未对准的图像中合成混合图像。在这项工作中，我们提出了一种新颖的方法，用于添加要从中距观看距离观看的图像。中频（MF）图像由特殊的带通滤波器提取，该滤波器在仅提取指定的频带时会产生振铃。用这种方法 从远处观察并接近时，中频应被视为无意义的模式。进行了参数调整实验，以确定用于设计MF图像滤波器的合适截止频率。我们发现，从远处观看时，可以使用适当大小的振铃使中频不那么明显。